arc: New Synopsys ARC port

arc: New Synopsys ARC port

ARC is a family of licensable processors developed by Synopsys.

This is an initial patch that doesn't yet support some of the features, that
are already available in Synopsys' fork of GDB, namely:

  * longjmp support
  * signal frame handling
  * prologue analysis
  * Linux targets support
  * native Linux support

ARC cores are configurable and extensible, which means from debugger
perspective that some registers and debug capabilities are optional, therefore
it is up to the GDB stub to determine exact list of register available on
target and supply it to GDB via XML target descriptions.  List of registers
that is known to GDB and is required is intentionally kept small to simplify
requirements to GDB stub and implementation of a GDB client.

gdb/ChangeLog:

	* Makefile.in (ALL_TARGET_OBS): Add arc-tdep.o.
	(HFILES_NO_SRCDIR): Add arc-tdep.h.
	(ALLDEPFILES): Add arc-tdep.c.
	* NEWS: Mention new ARC port.
	* configure.tgt: Add ARC.
	* arc-tdep.c: New file.
	* arc-tdep.h: New file.
	* features/Makefile (XMLTOC): Add arc-v2.xml and arc-arcompact.xml.
	* features/arc-v2.xml: New file.
	* features/arc-v2.c: New file (generated).
	* features/arc-arcompact.xml: New file.
	* features/arc-arcompact.c: New file (generated).

gdb/doc/ChangeLog:

	* gdb.texinfo (Embedded Processors): Document ARC.
	(Synopsys ARC): New section.
	(Standard Target Features): Document ARC features.
	(ARC Features): New section.

gdb/testsuite/ChangeLog:

	* gdb.xml/tdesc-regs.exp: set core-regs for arc*-*-elf32.